Method of coating wire



Patented Dec. 31, 1940 UNITED STATES PATENT OFFICE METHOD OF COATINGWIRE No Drawing. Application August 28, 1937, Serial No. 161,410

Claims.

The present invention relates to methods by means of which the surfaceof wire or other metal objects may be caused to adhere effectively torubber. More particularly, the invention relates to coated wires and themethod of manufacture thereof by means of which the wire may be causedto adhere effectively to rubber when it is imbedded therein.

This is a continuation in part of my application, Serial No. 45,784,filed October 19, 1935.

In the manufacture of vehicle tires, it is common to use a bead wire tomaintain the rimengaging portion of the tire constant in circumference,the wire being imbedded in a coating of rubber. One of the requirementsfor use in this connection is that the wire must adhere effectively tothe rubber, a condition which has proved diflicult to secure.

In accordance with the present invention it is proposed to provide awire, or other metal object, to the surface of which rubber may becaused to adhere efi'ectively.

A further object of the invention is to provide a wire, the surface ofwhich is formed in such fashion as to enable the wire to be imbedded in.

rubber, as, for example. when utilized as a bead wire for a vehicletire, the rubber adhering effectively to the surface of the wire.

A further object of the invention is to provide a method by means ofwhich the surface of a wire or other metal object may be treated tocause rubber to adhere efiectively thereto.

A further object of the invention is to provide a method by means ofwhich wire or other metal may be coated in such fashion as to causerubber to adhere effectively thereto.

A further object of the invention is to provide a method by means ofwhich wire or other metal may be caused to adhere effectively to rubberby providing on such wire or other metal a non-metallic coating, suchcoating preferably containing salts of certain metals.

Further objects of the invention will be apparent as it is described infurther detail and, in order that the invention may be more readilyunderstood, one specific embodiment thereof will now be described.

In order that the surface of the wire may be such as to cause rubber toadhere closely and effectively thereto, the wire is first cleanedthoroughly, as by pickling in an acid solution, and may then either betreated directly with the coating bath later described, or coated withzinc or cadmium. The zinc or cadmium may be applied in any desiredmaner, employing any of the methods now commonly used in coating wireand other objects. the particular manner in which the coating of zinc orcadmium is applied to the wire being of no importance insofar as thepresent invention is concerned. 5 The cleaned or zinc or cadmium coatedwire is immersed in a bath containing copper sulphate and ammoniummolybdate. The solution in which the coated wire is immersed thuscontains a salt or combination "of salts of heavy metals, coppersulphate and ammonium molybdate having been found to produceparticularly good results. A solution for coating the wire which hasbeen found to be exceptionally satisfactory is as fol- The abovedescribed coating bath may, of course, be varied by increasing ordecreasing the proportions of the various ingredients, as may be founddesirable.

The foregoing process forms, on the metallic surface which is to adhereto rubber, a film which apparently reacts with the sulphur contained asa binder in the rubber. It is believed that such reaction liberates asmall amount of sulphur which in turn combines with the metallic surfaceto form a continuous bond between the rubber and the surface.

It is to be noted that a factor of great importance in connection withthe present invention resides in the use of a non-metallic film on themetal surface, such film consisting of products of the reaction betweenthe metallic surface and the solutions into which the surface is dipped.The coating contains some copper and possibly slight traces ofmolybdenum, as well as salts of these metals. Actual analyses made ofthe zinc or cadmium coated wires having the coating above described showthe coating to be composed of copper and molybdenum and zinc or cadmiumsulphates, nitrites and sulphites. Since the solution is acidulated bynitric acid, nitrates of the metals are formed. It appears that somereaction takes place with the metallic coating of the wire reducing thenitrates to nitrites, thereby resulting in the presence of the abovenitrites. When the term coaction product of copper sulphate and ammoniummolybdate are used hereinafter in the specification or claims, the termwill be understood to embrace substantially the cured at 270 F. for 55minutes.

above" mentioned compounds and elements, combining the same inproportions varying with the treatment accorded the particular metal.

The adhesion values derived from connections of this character aretested by placing the coated wire or other metallic object in a suitablemold andintroducing raw rubber around it so that two inches of the wireare embedded in the rubber. The whole is then placed in a hydraulicpress and The rubber conforms to the size of the mold, which is 2" x 4".After the rubber and wire have been allowed to stand 24 hours, the wireis pulled out of the rubber, the number of pounds required to pull thewire from the rubber being the adhesion value obtained. Comparativetests on wire coated in the copper sulphate-ammonium molybdate bath andwith various other coating compositions gave the following results.Ordinary steel wire requires about 8 poundsywhile zinc coated wirerequires about 43 pounds. The type of coating obtained by immersion inthe copper-sulphateammonium molybdate' bath produces values in theneighborhood of 100 pounds. Copper sulphate, acidulated by sulphuricacid (about 5%) results in a value of about pounds, while coppersulphate solution made ammoniacal by the addition of 10 c. c. of ammoniaresults'in a value of about to pounds.

'It has been found, also, that wire coated in accordance with theabove-described process retains its adhesion value almost indefinitely.As is well known, copper or other metal coated wires tend to lose theiradhesiveness for rubber, either after vulcanizing, or deteriorate to apoint where no improved adhesive efiect over ordinary metal is obtained,if not promptly vulcanized to rubber.

While the invention has been described with specific reference to themethod and substances outlined above, it is obvious that similar andequivalent substances having like properties may be utilized withoutdeparting from the scope of the present invention, as defined in theappended claims.

I claim:

1. The process of vulcanizing rubber to a metal selected from the groupconsisting of zinc and cadmium, immersing the metal in an acidifiedsolution of copper sulphate and ammonium molybdate and vulcanizingrubber to the coated metal.

2. The process of vulcanizing rubber to metal comprising coating themetal with a metal selected from the group consisting of zinc andcadmium, the coating metal used differing from the coated metal,immersing the coated metal in an acidified solution of the reactionproducts produced by mixing about 5 parts copper sulphate, about 0.3part of molybdic acid and about 0.7 part of ammonia water andvulcanizing rubber to the coated metal.

3. The process of vulcanizlng rubber to metal comprising cleaning theobject, immersing the object in an aqueous solution prepared bydissolving about 5 parts of copper sulphate, about .3 part of molybdicacid in slightly ammoniacal water and acidifying said solution to form anonmetallic coating comprising a reaction product of said metal andsolution, drying the metallic object, and vulcanizing rubber to thecoated metal.

4. A method of making a rubber coated wire comprising forming on a wirecontaining a metal selected from the group consisting of zinc andcadmium, a non-metallic coating by immersing the wire in a bath preparedby dissolving copper sulphate and molybdic acid in a slightly ammoniacalaqueous solution and acidifying the solution, placing the coated wire ina. mold, introducing rubber around the wire in said mold and heatingunder pressure for a sufficient length of time to cure the rubber andcause it to adhere to said coated wire.

5. A rubber coated article comprising a metallic body, a metalliccoating thereon of copper and molybdenum, a metal selected from thegroup consisting of zinc and cadmium, a non-metallic coating consistingof the sulphates, sulphltu and nitrites of copper, molybdenum and saidmetal and a tightly adherent coating of rubber formed on saidnon-metallic coating.

BENJAMIN LEWIS MCCARTHY.

CERTIFICATE OF CORRECTION. Patent No. 2,226,958; December 1, 191w.

BENJAMIN LEWIS MCCARTHY.

It is hereby certified that .error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 2,second column, line 59, claim 5, strike out the comma and insert insteadthe word -and--; and that the said Letters Patent should be read withthis correction therein that the same may conform to the record of thecase in the Patent Qffice.

Signed and sealed this Lpth day of February, A. D. 19111.

Henry Van Arsdale (Seal) Acting comissioner of Patents.

